Vehicle and method for controlling vehicle

ABSTRACT

A vehicle is equipped with a battery, an electric motor configured so as to generate the driving force of the vehicle by use of the electric power stored in the battery, a charger configured so as to supply the electric power outputted from the power supply outside of the vehicle to the battery, and an ECU configured so as to control the state of charge of the battery when the battery is charged. The ECU calculates an index value indicating the state of charge of the battery, and sets the control range thereof. The ECU raises the upper limit of the index value so that the possible travel distance of the vehicle becomes not less than the target distance when predetermined conditions on degradation of the battery are satisfied.

TECHNICAL FIELD

The present invention relates to a vehicle and a method of controllingthe vehicle and, more specifically, to charge-control of a power storagedevice mounted on a vehicle.

BACKGROUND ART

Vehicles including hybrid vehicles, electric vehicles and fuel-cellvehicles include a power storage device for storing electric power andan electric motor. As the electric power is supplied from the powerstorage device to the electric motor, the electric motor generatesdriving force for driving the vehicle. At the time of braking, theelectric motor regenerates power. The regenerated electric power issupplied to the power storage device. Therefore, while the vehicle isrunning, charging and discharging of the power storage device arecontrolled such that an index value (SOC) indicating the state of chargeof the power storage device is within an appropriate range. SOC isdefined as a ratio of the current amount of charges with respect to theamount of charges in a fully charged state. SOC of the power storagedevice in the fully charged state is 100(%) and SOC of the power storagedevice not charged at all is 0(%).

By way of example, Japanese Patent Laying-Open No. 2004-56867 (PTL 1)discloses a hybrid vehicle control system in which control width of SOCof the power storage device is adjustable in accordance with travelingsections. The control system includes a road information acquiring unitacquiring road information of a scheduled travel route of the vehicle, acontrol width and traveling method determining unit for changing controlwidth of SOC of power storage means and for determining the method oftraveling of the vehicle, and a control processing unit for controllingtraveling of the vehicle in accordance with the determined method oftravel. The control width and traveling method determining unitcalculates SOC of the power storage means (battery) in a prescribedsection of the scheduled travel route of the vehicle, and based on theSOC, changes the control width of SOC. Further, the control width andtraveling method determining unit determines the method of traveling ofthe hybrid vehicle such that SOC at the end of prescribed section iswithin the control width.

By way of example, Japanese Patent Laying-Open No. 2005-65352 (PTL 2)discloses a controller for controlling charging/discharging of abattery. The controller changes control width of battery SOC to preventover-discharge of the battery, and avoids the influence of memory effecton charging/discharging of the battery. More specifically, thecontroller increases both the upper and lower limits of control width ofthe SOC, if memory effect occurs.

CITATION LIST Patent Literature

-   PTL 1: Japanese Patent Laying-Open No. 2.004-56867-   PTL 2: Japanese Patent Laying-Open No. 2005-65352

SUMMARY OF INVENTION Technical Problem

The cruising distance of vehicles described above should preferably beas long as possible. In the present specification, the “cruisingdistance” refers to a distance a vehicle can travel by the electricpower stored in the power storage device.

One solution to make longer the cruising distance is to increase thenumber of power storage devices or to increase the number of cellsforming the power storage device. If the number of power storage devicesor the number of cells increases, however, the volume and weight of thepower storage device or devices naturally increase and, in addition, thecost for the power storage device or devices increases. As the weight ofpower storage device increases, the actual cruising distance could beshorter than the distance calculated based on the capacity of the powerstorage device.

The controller disclosed in PTL 1 changes the control width of SOC whilethe hybrid vehicle is traveling, in order to recover sufficientregenerative current to the battery. This can reduce fuel consumption ofthe hybrid vehicle. PTL 1 discloses, however, only the technique forreducing fuel consumption for a vehicle traveling in a given period oftime.

While a hybrid vehicle travels repeatedly, the power storage devicedeteriorates gradually. When the power storage device deteriorates,capacity of the power storage device decreases. Therefore, as the hybridvehicle is used for longer years, it possibly becomes more difficult tosufficiently attain the effect of reducing fuel consumption. PTL 1 doesnot describe any specific method of preventing decrease in capacity ofthe power storage device.

PTL 2 describes a method of preventing decrease in battery capacitycaused by the memory effect. PTL 2, however, is silent about batterydeterioration caused when the vehicle travels repeatedly. In otherwords, PTL 2 does not disclose battery control considering batterydeterioration.

An object of the present invention is to provide a vehicle that canreduce deterioration of power storage device and ensure sufficientcruising distance.

Solution to Problem

According to an aspect, the present invention provides a vehicle,including: a power storage device configured to be rechargeable; anelectric motor configured to generate driving force for driving thevehicle by using electric power stored in the storage device; a chargingmechanism configured to supply electric power output from a power sourceoutside the vehicle to the power storage device; a command generatingunit configured to be switched between generation of a command to makelonger a useable period of the power storage device and stopping ofgeneration of the command, by a manual operation; and a controllerconfigured to control state of charge of the power storage device whenthe power storage device is charged. The controller includes a stateestimating unit configured to calculate an index value indicating thestate of charge, and a setting unit configured to increase an upperlimit value of the index value when prescribed condition related todeterioration of the power storage device is satisfied. The setting unitsets an amount of change of the upper limit value such that possibledistance of travel of the vehicle attains to a target distance orlonger.

Preferably, the setting unit is configured to make smaller the amount ofchange as the number of increase of the upper limit value increases.

Preferably, the setting unit is configured to increase the upper limitvalue repeatedly until the upper limit value reaches a standard value,and to maintain the upper limit value at the standard value once theupper limit value reached the standard value.

Preferably, the controller further includes a detecting unit configuredto detect any abnormality occurred in the power storage device. Thesetting unit is configured to lower the upper limit value when theabnormality is detected by the detecting unit.

Preferably, the controller further includes a detecting unit configuredto detect any abnormality occurred in the power storage device. Thesetting unit is configured to maintain the upper limit value at apresent value when the abnormality is detected by the detecting unit.

Preferably, the prescribed condition is determined in advance based onperiod of use of the vehicle.

Preferably, the prescribed condition is determined in advance based ontravel distance of the vehicle.

Preferably, the setting unit is capable of switching between a firstmode having the upper limit value fixed and a second mode allowingadjustment of the upper limit value, and sets the amount of change inthe second mode.

Preferably, the vehicle further includes a command generating unitconfigured to switch between generation of a command to extend a useableperiod of the power storage device and stopping of generation of thecommand, by a manual operation. The setting unit selects the second modefrom the first and second modes when the command generating unitgenerates the command, and selects the first mode from the first andsecond modes when the command generating unit stops generation of thecommand.

According to another aspect, the present invention provides a method ofcontrolling a vehicle. The vehicle includes a power storage deviceconfigured to be rechargeable, an electric motor configured to generatedriving force for driving the vehicle by using electric power stored inthe storage device, a charging mechanism configured to supply electricpower output from a power source outside the vehicle to the powerstorage device, a command generating unit configured to switch betweengeneration of a command to make longer a useable period of the powerstorage device and stopping of generation of the command, by a manualoperation, and a controller configured to control state of charge of thepower storage device when the power storage device is charged. Thecontrol method includes the steps of calculating an index valueindicating the state of charge, and increasing an upper limit value ofthe index value when prescribed condition related to deterioration ofthe power storage device is satisfied. At the step of increasing theupper limit value, an amount of change of the upper limit value is setsuch that possible distance of travel of the vehicle attains to a targetdistance or longer.

Preferably, the control method further includes the step of makingsmaller the amount of change as the number of increase of the upperlimit value increases.

Preferably, the control method further includes the step of limiting theupper limit value so that the upper limit value does not exceed astandard value when the upper limit value is increased repeatedly.

Preferably, the control method further includes the steps of detectingany abnormality occurred in the power storage device, and lowering theupper limit value when the abnormality is detected.

Preferably, the control method further includes the steps of detectingany abnormality occurred in the power storage device, and fixing theupper limit value at a present value when the abnormality is detected.

Preferably, the prescribed condition is determined in advance based onperiod of use of the vehicle.

Preferably, the prescribed condition is determined in advance based ontravel distance of the vehicle.

Preferably, the vehicle control method further includes the step ofselecting one of a first mode having the upper limit value fixed and asecond mode allowing adjustment of the upper limit value. At the step ofincreasing the upper limit value, the amount of change is set when thesecond mode is selected.

Preferably, the vehicle further includes a command generating unitconfigured to be switched between generation of a command to extend auseable period of the power storage device and stopping of generation ofthe command, by a manual operation. At the step of selecting, the secondmode is selected from the first and second modes when the commandgenerating unit generates the command, and the first mode is selectedfrom the first and second modes when the command generating unit stopsgeneration of the command.

Advantageous Effects of Invention

By the present invention, deterioration of a power storage devicemounted on the vehicle can be reduced, and sufficient cruising distanceof the vehicle can be ensured.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an overall block diagram of a vehicle in accordance withEmbodiment 1 of the present invention.

FIG. 2 shows an example of a configuration of a monitoring unit shown inFIG. 1.

FIG. 3 is a functional block diagram of a charge ECU shown in FIG. 1.

FIG. 4 is an illustration showing SOC control ranges in the normal modeand in the long life mode.

FIG. 5 is a flowchart representing control of battery charging executedby the charge ECU shown in FIG. 1.

FIG. 6 is a graph showing correlation between age of service of avehicle running with electric power stored in a lithium ion battery andcapacity maintenance ratio of the lithium ion battery.

FIG. 7 is a graph showing cruising distances in the long life mode andthe normal mode.

FIG. 8 shows a cruising distance that can be attained by the control inaccordance with an embodiment.

FIG. 9 is a graph representing control of an upper limit value ofcontrol range based on age of service of a battery 10.

FIG. 10 is a graph representing control of an upper limit value ofcontrol range based on travel distance of a vehicle 1.

FIG. 11 shows a first example of a table stored in a control rangesetting unit 111 shown in FIG. 3.

FIG. 12 shows a second example of a table stored in control rangesetting unit 111 shown in FIG. 3.

FIG. 13 is a flowchart representing a control executed in accordancewith the table shown in FIG. 11.

FIG. 14 is a flowchart representing a control executed in accordancewith the table shown in FIG. 12.

FIG. 15 is an overall block diagram of a vehicle in accordance withEmbodiment 2 of the present invention.

FIG. 16 is a functional block diagram of a charge ECU shown in FIG. 15.

FIG. 17 is a graph representing control of an upper limit value ofcontrol range in accordance with Embodiment 2.

FIG. 18 is a flowchart representing a control executed by the charge ECUshown in FIG. 15.

FIG. 19 is an overall block diagram of a vehicle in accordance withEmbodiment 3 of the present invention.

FIG. 20 is a functional block diagram of the charge ECU shown in FIG.19.

FIG. 21 is a graph representing control of an upper limit value ofcontrol range in accordance with Embodiment 3.

FIG. 22 is a flowchart representing a control executed by the charge ECUshown in FIG. 19.

FIG. 23 is a graph representing a first control executed whenabnormality of battery 10 is detected.

FIG. 24 is a flowchart representing the control shown in FIG. 23.

FIG. 25 is a graph representing a second control executed whenabnormality of battery 10 is detected.

FIG. 26 is a first flowchart representing the control shown in FIG. 25.

FIG. 27 is a second flowchart representing the control shown in FIG. 25.

FIG. 28 shows a configuration of a hybrid vehicle as an example of thevehicle in accordance with the present invention.

DESCRIPTION OF EMBODIMENTS

In the following, embodiments of the present invention will be describedin detail with reference to the figures. In the figures, the same orcorresponding portions are denoted by the same reference characters, anddescription thereof will not be repeated.

Embodiment 1

FIG. 1 is an overall block diagram of the vehicle in accordance withEmbodiment 1 of the present invention. Referring to FIG. 1, vehicle 1 inaccordance with Embodiment 1 of the present invention includes a battery10, a system main relay (hereinafter also referred to as “SMR”) 12, aninverter 16, a motor generator (hereinafter also referred to as “MG”)20, driving wheels 22, and an MG-ECU (Electronic Control Unit) 30.Vehicle 1 further includes a charge inlet 42, a sensor 43, a charger 44,a relay 46, a charge ECU 48, a switch 49, a current sensor 50, amonitoring unit 54 and an air conditioner 70.

Battery 10 is a power storage device configured to be rechargeable.Battery 10 consists of a battery assembly including a plurality of cells11 connected in series. In the present embodiment, battery 10 is alithium ion battery.

When vehicle 1 travels, battery 10 supplies electric power for drivingMG 20 to inverter 16. As the electric power stored in battery 10 issupplied to MG 20, MG 20 generates driving force for driving vehicle 1.At the time of braking of vehicle 1, electric power regenerated by MG 20is supplied to battery 10. When electric power is supplied to vehicle 1from a power source 60 provided outside of vehicle 1, charger 44supplies the electric power to battery 10. With the supplied electricpower, battery 10 is charged. Power source 60 is, for example, an ACpower source.

SMR 12 is provided between battery 10 and inverter 16. SMR 12 isconnected to battery 10 by a positive electrode line 13P and a negativeelectrode line 13N. SMR 12 is connected to inverter 16 by a positiveelectrode line 15P and a negative electrode line 15N. When vehicle 1 isrunning, SMR 12 is on. On the other hand, when battery 10 is charged bycharger 44, SMR 12 is off. SMR 12 may be provided between battery 10 andrelay 46.

Inverter 16 drives MG 20 based on a control signal PWI1 from MG-ECU 30.

Though not shown, inverter 16 is formed, for example, by a three-phasebridge circuit including U-phase, V-phase and W-phase arms. Inverter 16converts DC power output from battery 10 to AC power, and supplies theAC power to MG 20. Inverter 16 coverts AC power generated by MG 20 to DCpower and supplies the DC power to battery 10. For conversion betweenthe DC power for the battery and the DC power for the inverter, avoltage converter (DC/DC converter) may be provided between battery 10and inverter 16.

MG 20 is an AC rotating electrical machine, implemented, for example, bya three-phase AC synchronous electric motor having a rotor with apermanent magnet embedded. A rotation shaft of MG 20 is coupled todriving wheels 22. MG-ECU 30 generates control signal PWI1 for drivingMG 20, and outputs the control signal PWI1 to inverter 16.

Connector 62 is provided outside of vehicle 1, and connected to powersource 60. Charge inlet 42 is connected to the input side of charger 44and is configured to be connectable to connector 62. When charge inlet42 is connected to connector 62, the AC power from power source 60 isinput to charge inlet 42. Sensor 43 detects connection between chargeinlet 42 and connector 62, and outputs a signal STR indicating thatcharging of battery 10 can be started. When connector 62 is disconnectedfrom charge inlet 42, sensor 43 stops output of the signal STR.

Charger 44 is connected by means of relay 46 to positive electrode line13P and negative electrode line 13N, and supplies the electric poweroutput from power source 60 to battery 10. Charger 44 is formed, forexample, by an AC/DC converter converting AC power to DC power. Charger44 converts AC power supplied from power source 60 to DC power based ona control signal PWD from charge ECU 48. The DC power output fromcharger 44 is supplied through relay 46, positive electrode line 13P andnegative electrode line 13N to battery 10. While charger 44 is chargingbattery 10, relay 46 is kept on.

Charger 44 may be provided outside of vehicle 1. In that case, chargeinlet 42 receives the DC power output from charger 44. The electricpower input to charge inlet 42 is supplied through relay 46, positiveelectrode line 13P and negative electrode line 13N to battery 10. Inshort, charge inlet 42 and relay 46 supply electric power output frompower source 60 to battery 10.

Charge ECU 48 starts control of charger 44 based on the signal STR fromsensor 43. More specifically, charge ECU 48 generates a control signalPWD for driving charger 44 based on detected values of current, voltageand temperature transmitted from monitoring unit 54, and transmits thecontrol signal PWD to charger 44. Based on the control signal PWD,charger 44 converts the AC power supplied from power source 60 to DCpower.

Charge ECU 48 controls charger 44 based on an index value (SOC)indicating the state of charge of battery 10. When SOC of battery 10reaches the upper limit value of a control range, charge ECU 48 stopsoutput of control signal PWD. As the charge ECU 48 stops output ofcontrol signal PWD, charger 44 stops. As charger 44 stops, charging ofbattery 10 ends. SOC is defined as the ratio of the current amount ofcharges in battery 10 to the amount of charges in battery 10 in thefully charged state.

Switch 49 is mounted on vehicle 1 as a switch operated by a user. Bymanual operation, switch 49 can be switched to on-state and off-state.When switch 49 is on, switch 49 generates a command (signal SLF) forsetting a charging mode of battery 10 to reduce deterioration of battery10. As the deterioration of battery 10 is reduced, the period of use ofbattery 10 can be made longer. More specifically, the signal SLF is acommand to make longer the period of use of battery 10. In thefollowing, the charging mode for reducing deterioration of battery 10will be referred to as “long life mode.”

When the user turns off switch 49, switch 49 stops generation of signalSLF. Thus, setting of the long life mode is cancelled, and the chargingmode of vehicle 1 is switched from the long life mode to a normal mode.Specifically, by operating switch 49, the user can select the chargingmode of vehicle 1 from the long life mode and the normal mode.

Charge ECU 48 sets the control range of SOC for charging battery 10. Thecontrol range in the long life mode is narrower than the control rangein the normal mode. Specifically, the upper limit value of control rangein the long life mode is smaller than the upper limit value of controlrange in the normal mode. The lower limit value of control range in thelong life mode is equal to or higher than the lower limit value ofcontrol range in the normal mode. Specifically, charge ECU 48 controlsthe state of charge of battery 10 at the time of charging battery 10.

In the following, the “upper limit of control range” is also referred toas “upper limit value of SOC” or simply “upper limit value.”

Current sensor 50 detects a current input to battery 10 and a currentoutput from battery 10, and outputs an analog signal that changes inaccordance with the magnitude of current to monitoring unit 54.

Monitoring unit 54 converts the analog signal output from current sensor50 to a digital signal indicating a current value. Monitoring unit 54outputs the digital signal (current value) to charge ECU 48. Further,monitoring unit 54 detects temperature and voltage of each battery blockconsisting of a prescribed number of cells 11. Monitoring unit 54outputs digital signals representing the temperature and voltage of eachblock to charge ECU 48.

Auxiliary machinery that operates with the electric power supplied frombattery 10 is connected to positive electrode line 13P and negativeelectrode line 13N. FIG. 1 shows air conditioner 70 as a representativeexample of auxiliary machinery.

FIG. 2 shows an example of a configuration of a monitoring unit shown inFIG. 1. Referring to FIG. 2, battery 10 includes a plurality ofseries-connected cells 11. The plurality of cells 11 is divided into aplurality of battery blocks BB(1) to BB(n) (n: natural number).Monitoring unit 54 includes a group of sensors 56(1) to 56(n) arrangedcorresponding to battery blocks BB(1) to BB(n), respectively, and ananalog-digital converter (A/D) 58 arranged corresponding to currentsensor 50.

Each of the sensors 56(1) to 56(n) detects the temperature and voltageof the corresponding block. Sensors 56(1) to 56(n) detect temperaturesTb(1) to Tb(n), respectively. Further, sensors 56(1) to 56(n) detectvoltages Vb(1) to Vb(n), respectively. Detected values of sensors 56(1)to 56(n) are output to charge ECU 48.

Analog-digital converter 58 converts an analog signal from currentsensor 50 to a digital signal. The digital signal indicates the value ofcurrent Ib. The current Ib represents the current input to battery 10and the current output from battery 10.

In addition to the group of sensors 56(1) to 56(n) and analog-digitalconverter (A/D) 58 shown in FIG. 2, a monitor for monitoring voltage ofcell 11 may be provided for each cell 11. Each monitor turns on a flagindicating abnormality of the cell, if the voltage of corresponding cellis out of a normal range. If any flag is turned on, charge ECU 48 candetect abnormality of battery 10.

FIG. 3 is a functional block diagram of a charge ECU shown in FIG. 1.Referring to FIG. 3, charge ECU 48 includes an SOC estimating unit 101,a control range setting unit 111, a determining unit 112 and a signalgenerating unit 113.

SOC estimating unit 101 receives detected values of current Ib, voltagesVb(1) to Vb(n) and temperatures Tb(1) to Tb(n), from monitoring unit 54.Based on each of the detected values, SOC estimating unit 101 calculatesSOC of battery 10 as a whole. More specifically, SOC estimating unit 101calculates, based on the detected values of each block, the SOC of thecorresponding block, and based on the SOC of each block, calculates theoverall SOC. In the present embodiment, a known method of calculatingSOC of a lithium ion battery can be used for calculating SOC of eachblock. By way of example, SOC of each block may be calculated based onaccumulated value of current Ib. Alternatively, SOC of each block may becalculated at a constant interval, based on correlation betweenopen-circuit voltage (OCV) and SOC and on the voltage value detected bymonitoring unit 54. The method of calculating the overall SOC from theSOC of each block is not specifically limited. For instance, the overallSOC may be an average value of SOC of the blocks.

Control range setting unit 111 sets the control range of SOC. If theswitch 49 is off, switch 49 stops generation of signal SLF. Here,control range setting unit 111 sets the SOC control range to a firstrange, and outputs an upper limit value UL1 for the first range. On theother hand, if the user turns on switch 49, switch 49 generates signalSLF. Here, control range setting unit 111 sets the SOC control range toa second range and outputs an upper limit value UL2 for the secondrange. The first range represents the control range of SOC in the normalmode. The second range represents the control range of SOC in the longlife mode.

Determining unit 112 receives SOC from SOC estimating unit 101, andreceives either the upper limit value UL1 or UL2 from control rangesetting unit 111. Determining unit 112 determines whether or not SOCreached the upper limit value (UL1 or UL2). Determining unit 112 outputsthe result of determination to signal generating unit 113.

Signal generating unit 113 generates control signal PWD based on thesignal STR from sensor 43. Signal generating unit 113 outputs thecontrol signal PWD to charger 44. If it is determined by determiningunit 112 that SOC has reached the upper limit value, signal generatingunit 113 stops generation of control signal PWD based on the result ofdetermination by determining unit 112. As the generation of controlsignal PWD stops, charger 44 stops. As charger 44 stops, charging ofbattery 10 ends.

FIG. 4 is an illustration showing SOC control ranges in the normal modeand in the long life mode. Referring to FIG. 4, the first range R1 isthe control range of SOC in the normal mode. The second range R2 is thecontrol range of SOC in the long mode. UL1 represents the upper limitvalue of first range R1, and UL2 represents the upper limit value ofsecond range R2.

The lower limit value of first range R1 and the lower limit value ofsecond range R2 are both LL. It is noted, however, that the lower limitvalue of second range R2 may be higher than the lower limit value offirst range R1. Upper limit value UL2 is smaller than upper limit valueUL1. Therefore, the second range R2 is narrower than the first range R1.In order to prevent overcharge of battery 10, upper values UL1 and UL2are both smaller than 100(%). In order to prevent over-discharge ofbattery 10, the lower limit value LL is larger than 0(%).

FIG. 5 is a flowchart representing control of battery charging executedby the charge ECU shown in FIG. 1. The process of the flowchart isexecuted at every prescribed interval, or every time prescribedconditions are satisfied.

Referring to FIG. 5, at step S1, charge ECU 48 determines whether or notthe signal STR is generated. If signal generating unit 113 receives thesignal STR, signal generating unit 113 determines that the signal STR isgenerated. In this case (YES at step S1), the process proceeds to stepS2. On the other hand, if signal generating unit 113 does not receivethe signal STR, signal generating unit 113 determines that the signalSTR is not generated. Then (NO at step S1), the process returns to themain routine.

At step S2, charge ECU 48 determines whether or not the signal SLF isgenerated. If control range setting unit 111 does not receive the signalSLF, control range setting unit 111 determines that the signal SLF isnot generated. Then (NO at step S2), the process proceeds to step S3. Onthe other hand, if control range setting unit 111 receives the signalSLF, control range setting unit 111 determines that the signal SLF isgenerated. Then (YES at step S2), the process proceeds to step S4.

At step S3, charge ECU 48 (control range setting unit 111) sets theupper limit value of SOC control range to UL1. Thus, the charging modeis set to the normal mode. At step S4, charge ECU 48 (control rangesetting unit 111) sets the upper limit value of SOC control range toUL2. Thus, the charging mode is set to the long life mode. The upperlimit value (UL1 or UL2) set by control range setting unit 111 istransmitted from control range setting unit 111 to determining unit 112.

After the process of step S3 or S4, the process of step S5 is executed.At step S5, charge ECU 48 (signal generating unit 113) generates thecontrol signal PWD. Based on the control signal PWD, charger 44 convertsthe AC power supplied from power source 60 to DC power. As the DC poweris supplied from charger 44 to battery 10, battery 10 is charged.

At step S6, charge ECU 48 calculates SOC of battery 10. Morespecifically, SOC estimating unit 101 calculates the overall SOC ofbattery 10 based on the current value Ib, voltage values Vb(1) to Vb(n)and temperatures Tb(1) to Tb(n) transmitted from monitoring unit 54.

At step S7, charge ECU 48 determines whether or not SOC has reached theupper limit value (UL1 or UL2). More specifically, at step S7,determining unit 112 compares the SOC calculated by SOC estimating unit101 with the upper limit. Based on the result of comparison, determiningunit 112 determines whether or not SOC has reached the upper limitvalue.

If it is determined that SOC has reached the upper limit value (YES atstep S7), the process proceeds to step S8. On the other hand, if it isdetermined that SOC has not yet reached the upper limit value (NO atstep S7), the process returns to step S5. Until SOC reaches the upperlimit value, the process of steps S5 to S7 is executed repeatedly tocharge battery 10.

At step S8, charge ECU 48 stops generation of the control signal PWD.More specifically, if it is determined by determining unit 112 that SOChas reached the upper limit value, signal generating unit 113 stopsgeneration of control signal PWD based on the result of determination bydetermining unit 112. As a result, charging of battery 10 ends. If theprocess of step S8 ends, the overall process is returned to the mainroutine.

Vehicle 1 shown in FIG. 1 travels using the electric power stored inbattery 10. In order to make longer the cruising distance of vehicle 1,it is necessary to take out as much power as possible from battery 10.If the capacity of battery 10 is increased, the amount of electric powertaken out from battery 10 can be increased. Increase in batterycapacity, however, possibly leads to increased weight and volume ofbattery 10.

In the present embodiment, the upper limit of SOC at the time ofcharging battery 10 is set as high as possible. More specifically, theupper limit value is determined in advance such that battery 10 is notovercharged when SOC reaches the upper limit value. On the other hand,the lower limit value (LL) of SOC is determined in advance as a valuefor preventing over-discharge of battery 10. Thus, it becomes possibleto take out much electric power from battery 10. Thus, the cruisingdistance of vehicle 1 can be made longer.

Further, in the present embodiment, lithium ion battery is used asbattery 10. Lithium ion battery is characterized by high energy density.As lithium ion battery is mounted on vehicle 1, it becomes possible totake out much electric power from battery 10, and the size and weight ofbattery 10 can be reduced.

If the lithium ion battery is kept at high SOC state (for example, fullycharged state) for a long time, however, the characteristics of lithiumion battery deteriorate. For example, the capacity of lithium ionbattery decreases. By keeping lithium ion battery in low SOC state,deterioration of characteristics of lithium ion battery can be reduced.

FIG. 6 is a graph showing correlation between age of service of avehicle running with electric power stored in a lithium ion battery andcapacity maintenance ratio of the lithium ion battery. Referring to FIG.6, the capacity maintenance ratio when a lithium ion battery isbrand-new is defined to be 100(%). As the vehicle travels repeatedly,the lithium ion battery deteriorates gradually. As the age of service ofthe vehicle becomes longer, the capacity maintenance ratio decreases.Namely, the capacity of lithium ion battery lowers. As the SOC at theend of charging of lithium ion battery is higher, the degree of decreaseof capacity maintenance ratio to the age of service increases.

The period from the end of charging until start of traveling of vehicle1 may differ user by user. Therefore, it is possible that battery 10 iskept at the high SOC state for a long time. If battery 10 is kept athigh SOC state for a long time, the capacity of battery 10 may possiblydecrease.

In the present embodiment, vehicle 1 has the long life mode for makinglonger the duration of battery 10. When the long life mode is set, SOCcontrol range becomes narrower. More specifically, the upper limit valueof control range is made lower. Since the control range of SOC becomesnarrower, SOC at the completion of charging of battery 10 can be madelower. Thus, decrease in capacity of battery 10 can be reduced.

As the decrease in capacity of battery 10 is reduced, decrease incruising distance of vehicle 1 can also be reduced. As a result,sufficient cruising distance of vehicle 1 can be ensured. By way ofexample, after a target age of service is reached, the vehicle cantravel the target distance.

FIG. 7 is a graph showing cruising distances in the long life mode andthe normal mode. Referring to FIG. 7, if the degree of deterioration ofbattery 10 is small, battery 10 can store much electric power.Therefore, while the age of service of vehicle 1 is short, the cruisingdistance in the normal mode is longer than that in the long life mode.

If battery 10 is charged to nearly full, however, deterioration ofbattery 10 intensifies. Particularly, if battery 10 is new and SOC ofbattery 10 is high, deterioration of battery 10 proceeds rapidly. Ifbattery 10 is charged in the normal mode, the capacity of battery 10decreases in a large degree.

On the other hand, if battery 10 is charged in the long life mode, itcan slow down deterioration of battery 10. Thus, by charging battery 10in the long life mode, decrease in capacity of battery 10 can bereduced. As shown in FIG. 7, if the age of service of vehicle 1 becomeslonger, the cruising distance in the long life mode can be made longerthan that in the normal mode. Specifically, by charging battery 10 inthe long life mode, deterioration of battery 10 can be reduced andlonger cruising distance of vehicle 1 can be ensured.

Further, according to the present embodiment, vehicle 1 has switch 49that is operated by the user. By operating switch 49, the user canselect the charging mode of battery 10 from the normal mode and the longlife mode. If the long life mode is selected, deterioration of battery10 can be reduced and, hence, even after the age of service becomeslonger, sufficient cruising distance can be ensured. On the other hand,if battery 10 has sufficient margin in its performance (when the age ofservice is short) and the normal mode is selected, the amount of chargesof battery 10 can be increased and, therefore, higher travelingperformance of vehicle 1 can be attained. For example, vehicle cantravel longer distance than normal cruising distance.

According to the present embodiment, since the user can select thecharging mode from the normal mode and the long life mode, conveniencefor the user can be improved.

The control range of SOC during traveling is set independently from thecontrol range at the time of charging battery 10. By way of example, atthe time of braking of vehicle 1, SOC increases as battery 10 is chargedby regenerative power from MG 20. As a result, SOC possibly becomeshigher than the upper limit value at the time of charging of battery 10.SOC, however, lowers again as vehicle 1 continuously travels.Specifically, while vehicle 1 is traveling, it is not likely thatbattery 10 is kept at the high SOC state for a long time. Therefore, thecontrol range of SOC during traveling can be set independent from thecontrol ranges in the long life mode and in the normal mode.

It is noted, however, that even if the long life mode is selected as thecharging mode, battery 10 deteriorates as the age of service of battery10 becomes longer. Therefore, as the age of service of vehicle 1 becomeslonger, the cruising distance becomes shorter. Therefore, in the presentembodiment, the upper limit value (UL2) of the SOC control range isincreased if the long life mode is selected as the charging mode andprescribed conditions related to deterioration of battery 10 aresatisfied.

FIG. 8 shows a cruising distance that can be attained by the control inaccordance with the present embodiment. Referring to FIG. 8, the upperlimit value of the SOC control range increases at a prescribed timingbased on the state of deterioration of battery 10. If the upper limitvalue is fixed, the cruising distance only decreases (see dotted line201). On the other hand, by increasing the upper limit value, the amountof charges in battery 10 can be increased (see solid line 202). Thus,the cruising distance can be increased.

Because of deterioration of battery 10, capacity of battery 10decreases. If the upper limit value of the control range of SOC isfixed, the amount of electric power that can be taken out from battery10 decreases as the age of service becomes longer. Therefore, asindicated by the dotted line, as the age of service becomes longer, thecruising distance becomes shorter. In accordance with the presentembodiment, as the upper limit value of the control range is increasedat an appropriate timing, the cruising distance can be made longer.Thus, the target cruising distance can be ensured when, for example, thetarget age of service is reached.

Causes of deterioration of battery 10 are the age of service of battery10 and travel distance of vehicle 1. Therefore, in the presentembodiment, the upper limit of the control range is changed based on atleast one of the age of service of battery 10 and the travel distance ofvehicle 1. In the following, the control of upper limit value based onthe age of service of battery 10 and the control of upper limit valuebased on the travel distance will be described.

FIG. 9 is a graph representing control of an upper limit value ofcontrol range based on age of service of battery 10. Referring to FIG.9, every time the age of service of battery 10 attains prescribed years(y₀), the upper limit value UL2 increases.

FIG. 10 is a graph representing control of an upper limit value ofcontrol range based on travel distance of vehicle 1. Referring to FIG.10, every time the travel distance of the vehicle reaches a prescribeddistance (x0), the upper limit value UL2 increases.

The control pattern of upper limit value UL2 shown in FIG. 9 or FIG. 10is stored as a map or a table in control range setting unit 111. Controlrange setting unit 111 changes the upper limit value UL2 of the controlrange in accordance with the map or the table. Each of FIGS. 9 and 10shows a control pattern of increasing upper limit value UL2 based oneither one of the travel distance and the age of service. In the presentembodiment, the upper limit value UL2 may be increased based both on thetravel distance and the age of service. Specifically, when the age ofservice of the battery reached a prescribed value, or when the traveldistance reached a prescribed distance, the upper limit value UL2 of SOCcontrol range may be increased. It is noted, however, that the upperlimit value UL2 is smaller than upper limit value UL1.

Control range setting unit 111 calculates the travel distance of thevehicle based on the velocity of the vehicle detected, for example, by avehicle speed sensor, not shown. Further, control range setting unit 111measures the period in which the vehicle speed is not 0, as the age ofservice of the vehicle. The methods mentioned above are examples ofmeasuring the travel distance and the age of service of the vehicle. Thetravel distance and the age of service of the vehicle may be measured byvarious known methods.

If battery 10 is much deteriorated, however, the capacity of battery 10decreases to a large degree. As described above, SOC represents theratio of current amount of charges to the amount of charges in the fullycharged state. Therefore, when battery 10 is much deteriorated, thecruising distance may not reach the target value if battery 10 ischarged to the upper limit value of SOC.

Therefore, charge ECU 48 (control range setting unit 111) increases theupper limit value UL2 to a value that can ensure the target cruisingdistance. The amount of change of upper limit value UL2 is determined byan experiment of repeating charging and discharging of the battery inaccordance with standard travel pattern of vehicle 1. The map or tablestored in control range setting unit 111 is determined based on theamount of change in the upper limit value obtained through theexperiment. In the following descriptions, control range setting unit111 stores the table for defining the upper limit value.

FIG. 11 shows a first example of a table stored in a control rangesetting unit 111 shown in FIG. 3. Referring to FIG. 11, the upper limitvalue (1) represents the original upper limit value, and the upper limitvalue (2) is a value after the upper limit value (1) is increased. Thecombination of upper limit values (1) and (2) is determined in advancefor every prescribed number of years y₀.

By way of example, if the age of service reaches the year y₀, the upperlimit value of SOC increases from ULa to ULb. The amount of change ofthe upper limit value is (ULb−ULa). As battery 10 deteriorates, thecruising distance of vehicle 1 gradually decreases. The amount of change(ULb−ULa) is set such that the cruising distance after the age ofservice reached the year y₀ is equal to or longer than the target value.

While the age of service is from the year y₀ to 2y₀, the upper limitvalue of SOC is kept at ULb. In this period, the cruising distancedecreases gradually. When the age of service reaches the year 2y₀, theupper limit value of SOC increases from ULb to ULc. The amount of changeof upper limit value is (ULc−ULb). As the upper limit value increases,the cruising distance again increases. Though (ULc−ULb) is equal to(ULb−ULa), it may be different from (ULb−ULa).

While the age of service is from the year 2y₀ to 3y₀, the upper limitvalue of SOC is kept at ULc. When the age of service reaches the year3y₀, the upper limit value of SOC increases from ULc to ULd.

FIG. 12 shows a second example of a table stored in control rangesetting unit 111 shown in FIG. 3. Referring to FIG. 12, every time thetravel distance reaches a prescribed distance x₀, the upper limit valueof SOC increases. Thus, as when the table shown in FIG. 11 is used, thetarget cruising distance can be ensured.

FIGS. 8 to 12 show control patterns in which the upper limit value isincreased a number of times. The number of increasing the upper limitvalue may be once. The number of increasing the upper limit value may bedetermined, for example, based on a standard age of service of vehicle1, capacity of battery 10 or the target cruising distance.

FIG. 13 is a flowchart representing a control executed in accordancewith the table shown in FIG. 11. The process of the flowchart isexecuted if the long life mode is set (step S4 of FIG. 5), at everyprescribed time interval, or when prescribed conditions are satisfied.

Referring to FIG. 13, at step S101, charge ECU 48 determines whether ornot the age of service of battery 10 has reached a standard value (y₀).Charge ECU 48 (control range setting unit 111) measures, for example,the years of travel of vehicle 1. The measured value is used as the ageof service of battery 10. If the measured value reaches the standardvalue (y₀), charge ECU 48 (control range setting unit 111) determinesthat the age of service of battery 10 has reached the standard value.

If it is determined that the age of service of battery 10 has reachedthe standard value (YES at step S101), the process proceeds to stepS102. On the other hand, if it is determined that the age of service ofbattery 1 has not yet reached the standard value (NO at step S101), theprocess proceeds to step S104.

At step S102, charge ECU 48 (control range setting unit 111) increasesthe upper limit value UL2. Here, control range setting unit 111 sets theupper limit value UL2 in accordance with the table shown in FIG. 11.Thus, upper limit value UL2 increases. Following the process of stepS102, the process of step S103 is executed.

At step S103, charge ECU 48 (control range setting unit 111) returns themeasured value of years of travel of vehicle 1 to 0. If the process atstep S103 ends, the overall process returns to the main routine.

At step S104, charge ECU 48 (control range setting unit 111) preventsincrease of upper limit value UL2. Namely, the upper limit value UL2 isnot changed. If the process at step S104 ends, the overall processreturns to the main routine.

FIG. 14 is a flowchart representing a control executed in accordancewith the table shown in FIG. 12. The process of the flowchart isexecuted if the long life mode is set (step S4 of FIG. 5), at everyprescribed time interval, or when prescribed conditions are satisfied.

Referring to FIG. 14, at step S101A, charge ECU 48 (control rangesetting unit 111) determines whether or not the travel distance ofvehicle 1 has reached the standard value (x₀). If it is determined thatthe travel distance of vehicle 1 has reached the standard value (YES atstep S101A), the process proceeds to step S102A. On the other hand, ifit is determined that the travel distance of vehicle 1 has not yetreached the standard value (NO at step S101A), the process proceeds tostep S104A.

At step S102A, charge ECU 48 (control range setting unit 111) increasesthe upper limit value UL2. Here, control range setting unit 111 sets theupper limit value UL2 in accordance with the table shown in FIG. 12.Thus, upper limit value UL2 increases. Following the process at stepS102A, the process of step S103A is executed.

At step S103A, charge ECU 48 (control range setting unit 111) returnsthe measured value of travel distance of vehicle 1 to 0. If the processat step S103A ends, the overall process returns to the main routine.

At step S104A, charge ECU 48 (control range setting unit 111) preventsincrease of upper limit value UL2. Namely, the upper limit value UL2does not change. If the process at step S104A ends, the overall processreturns to the main routine.

As described above, according to Embodiment 1, if prescribed conditionsrelated to deterioration of the battery are satisfied, the charge ECUincreases the upper limit value (UL2) of the SOC control range in thelong life mode. The amount of change in the upper limit value isdetermined in advance such that the cruising distance of vehicle 1attains to the target value or longer. Therefore, decrease in cruisingdistance can be prevented at least when the travel distance becomeslonger or when the age of service becomes longer. The upper limit value(UL2) is smaller than the upper limit value (UL1) when battery 10 ischarged in the normal mode. Therefore, the effect of reducingdeterioration of battery 10 can be attained.

Embodiment 2

FIG. 15 is an overall block diagram of a vehicle in accordance withEmbodiment 2 of the present invention. Referring to FIGS. 15 and 1, avehicle 1A is different from vehicle 1 in that it includes a charge ECU48A in place of charge ECU 48.

When the long life mode SOC is set as the charging mode and prescribedcondition related to deterioration of battery 10 is satisfied, chargeECU 48A increases the upper limit value of SOC control range. Further,charge ECU 48A stores the number of increase of upper limit value UL2.If the number is one or more, charge ECU makes smaller the mount ofchange of upper limit value UL2 this time than the amount of change lasttime. For example, when the upper limit value UL2 is increased thesecond time, the amount of change of upper limit value UL2 is smallerthan the amount of change when the upper limit value UL2 was increasedfor the first time.

FIG. 16 is a functional block diagram of a charge ECU shown in FIG. 15.Referring to FIGS. 16 and 3, charge ECU 48A is different from charge ECU48 in that it includes a control range setting unit 111A in place ofcontrol range setting unit 111.

Control range setting unit 111A stores the number the upper limit valueUL2 was increased in the past. If the number is one or more, it meansthat control for increasing the upper limit value UL2 has been executed.If the number of increase of upper limit value UL2 is one or more andthe prescribed condition related to deterioration of battery 10 issatisfied, control range setting unit 111A increases the upper limitvalue UL2 with the amount of change of upper limit value UL2 madesmaller than the amount of change last time.

As in Embodiment 1 above, control range setting unit 111A increases theupper limit value UL2 at least when the age of service of the vehiclereaches the standard value (y₀) or when the travel distance of thevehicle reaches the standard value (x₀). In the following, control ofcharge ECU 48A when the age of service of the vehicle has reached thestandard value (y₀) will be described as a representative.

FIG. 17 is a graph representing control of an upper limit value ofcontrol range in accordance with Embodiment 2. Referring to FIG. 17,when the age of service reaches the year y₀, the upper limit value UL2of SOC increases. The amount of change of upper limit value UL2 here isa1. When the age of service reaches the year 2y₀, the upper limit valueUL2 of SOC increases. The amount of change of upper limit value UL2 hereis a2 (<a1). When the age of service reaches the year 3y₀, the upperlimit value UL2 of SOC increases. The amount of change of upper limitvalue UL2 here is a3 (<a2).

By way of example, charge ECU 48A stores the relation between the age ofservice and the upper limit value shown in FIG. 17 as a map (or atable).

FIG. 18 is a flowchart representing a control executed by the charge ECUshown in FIG. 15. The process shown in the flowchart is executed atevery prescribed interval or every time prescribed conditions aresatisfied.

Referring to FIGS. 18 and 13, the flowchart shown in FIG. 18 isdifferent from the flowchart of FIG. 13 in that the process of stepsS111 to S113 is added.

If it is deter mined that the age of service of battery 10 has reachedthe standard value (YES at step S101), the process proceeds to stepS111. At step S111, charge ECU 48A (control range setting unit 111)determines whether or not the number of increase of upper limit valueUL2 is one or more. The number of times represents the number up to thepresent time.

If the number of increase of upper limit value UL2 is one or more (YESat step S111), the process proceeds to step S112.

At step S112, control range setting unit 111A makes the amount of changeof the upper limit value this time to be smaller than the amount ofchange last time. For instance, control range setting unit 111A uses avalue obtained by multiplying the amount of change last time by aprescribed constant as the amount of change this time. The constant is avalue larger than 0 and smaller than 1 and, by way of example, it is ½.By way of example, control range setting unit 111A may calculate theamount of change this time by subtracting a prescribed value from thelast amount of change. Further, control range setting unit 111A storesthe amount of change this time. The amount of change is used when theupper limit value UL2 is increased next time.

On the other hand, if the number of increase of the upper limit valueUL2 is 0 (NO at step S111), the process proceeds to step S113. Here, thecontrol for increasing the upper limit value UL2 has not been executedin the past. Therefore, there is no amount of change of the last time.Here, control range setting unit 111A uses an initial value as theamount of change this time.

After the process of step S112 or S113 is executed, the process of stepS102 is executed. At step S102, control range setting unit 111Aincreases the upper limit value UL2 in accordance with the map, forexample, shown in FIG. 17.

The process of steps S101, S102, S103 and S104 shown in FIG. 18 may bereplaced by the process of steps S101A, S102A, S103A and S104A shown inFIG. 14, respectively. Here, when the travel distance of the vehiclereaches the standard value (x₀), charge ECU 48A increases the upperlimit value UL2. Further, charge ECU 48A (control range setting unit111A) makes smaller the amount of change of the upper limit value thanthe amount of change last time.

If the age of service of vehicle 1 becomes longer, or if the traveldistance of vehicle 1 becomes longer, it is possible that the controlfor increasing the upper limit value UL2 be executed a number of times.If the amount of change is the same each time, the SOC at the completionof charging of battery 10 becomes high, since the upper limit value isincreased repeatedly. Then, battery 10 comes to be kept at high SOC and,hence, deterioration of battery 10 may possibly be intensified.

By Embodiment 2, similar effects as in Embodiment 1 can be attained.Further, by Embodiment 2, excessive increase of upper limit value UL2 inthe long life mode can be prevented. For instance, it is possible toprevent the upper limit value UL2 in the long life mode from exceedingthe upper limit value UL1 in the normal mode. Since the upper limitvalue UL2 is smaller than the upper limit value UL1, the effect ofreducing battery deterioration can be attained, even if the upper limitvalue UL2 is increased.

Embodiment 3

FIG. 19 is an overall block diagram of a vehicle in accordance withEmbodiment 3 of the present invention. Referring to FIGS. 19 and 1, avehicle 1B is different from vehicle 1 in that it includes a charge ECU48B in place of charge ECU 48.

Charge ECU 48B increases the upper limit value UL2 of SOC control rangeevery time prescribed conditions related to deterioration of battery 10are satisfied. It is noted that the upper limit value UL2 is set not toexceed a standard value. The standard value is determined in advance asa value that can prevent overcharging of battery 10.

Overcharging of battery 10 leads to a phenomenon causing deteriorationof performance of battery 10. By way of example, metal lithiumprecipitates at the negative electrode of cell 11. Therefore,overcharging of battery 10 must be prevented. If the performance of acell 11 lowers, the voltage of a battery block including the cell 11possibly lowers.

FIG. 20 is a functional block diagram of the charge ECU shown in FIG.19. Referring to FIGS. 20 and 3, charge ECU 48B is different from chargeECU 48 in that it additionally includes an abnormality detecting unit121. Further, charge ECU 48B is different from charge ECU 48 in that itincludes a control range setting unit 111B in place of control rangesetting unit 111A.

Abnormality determining unit 121 detects any abnormality of battery 10based on the voltage, current and temperature of battery 10 detected bymonitoring unit 54. By way of example, if at least one of voltage valuesVb(1) to Vb(n) output from monitoring unit 54 is different from a normalvalue, abnormality detecting unit 121 detects abnormality of battery 10.

As described above, a monitor for monitoring voltage of cell 11 may beprovided for each cell 11. By such a configuration, abnormalitydetermining unit 121 can detect any abnormality of battery 10 based onthe results of monitoring by the monitors.

As in Embodiment 1, control range setting unit 111B increases the upperlimit value UL2 at least when the age of service of the vehicle reachesa standard value (y₀) or when the travel distance of the vehicle reachesa standard value (x₀). It is noted, however, that the maximum number ofincreasing the upper limit value is determined in advance. When thenumber of increase of the upper limit value has reached the maximumvalue, the upper limit value reaches the standard value. Therefore, ifthe number of increase of the upper limit value has reached the maximumvalue mentioned above, control range setting unit 111B does not furtherincrease the upper limit value. Therefore, the upper limit value is keptat the standard value. In the following, control by charge ECU 48 whenthe age of service of the vehicle has reached the standard value (y₀)will be described as a representative.

FIG. 21 is a graph representing control of an upper limit value ofcontrol range in accordance with Embodiment 3. Referring to FIG. 21, atevery y₀ years, the upper limit value UL2 increases. In the exampleshown in FIG. 21, when the age of service reached the year 4y₀, theupper limit value UL2 becomes equal to the standard value Urn.Specifically, the maximum number of increase of upper limit value UL2 is4. After the year 4y₀, the upper limit value UL2 is kept at Um. By wayof example, charge ECU 48B stores the relation between the age of useand the upper limit value shown in FIG. 21 as a map (or a table).

FIG. 22 is a flowchart representing a control executed by the charge ECUshown in FIG. 19. The process shown in the flowchart is executed atevery prescribed interval or every time prescribed conditions aresatisfied.

Referring to FIGS. 22 and 13, the flowchart shown in FIG. 22 isdifferent from the flowchart of FIG. 13 in that it additionally includesthe process of step S121. If it is determined that the age of service ofbattery 10 has reached the standard value (YES at step S101), theprocess proceeds to step S121.

At step S121, charge ECU 48B determines whether or not it is possible toincrease the upper limit value UL2. By way of example, if the number ofincrease of upper limit value UL2 has not yet reached the maximumnumber, control range setting unit 111B determines that increase ofupper limit value UL2 is possible. In this case (YES at step S121), theprocess proceeds to step S102. At step S102, control range setting unit111B increases the upper limit value UL2 in accordance with the mapshown, for example, in FIG. 21.

On the other hand, if the number of increase of upper limit value UL2has already reached the maximum value (NO at step S121), the processproceeds to step S104. Here, control range setting unit 111B preventsincrease of upper limit value UL2. Thus, the upper limit value UL2 iskept at the standard value (Um).

The process of steps S101, S102, S103 and S104 shown in FIG. 22 may bereplaced by the process of steps S101A, S102A, S103A and S104A shown inFIG. 14, respectively. Here, when the travel distance of the vehiclereaches the standard value (x₀), charge ECU 48B increases the upperlimit value UL2. Further, charge ECU 48B (control range setting unit111B) limits the upper limit value UL2 such that the upper limit valueUL2 does not exceed the standard value.

Further, if any abnormality of battery 10 is detected by abnormalitydetermining unit 121, control range setting unit 111B sets the upperlimit value in accordance with a prescribed control pattern, so as notto intensify deterioration of battery 10. In the following, two controlpatterns applicable to an embodiment of the present invention will bedescribed.

(First Control Pattern)

FIG. 23 is a graph representing a first control executed whenabnormality of battery 10 is detected. Referring to FIG. 23, if the ageof service of vehicle 1B reaches the year y₀, the upper limit value UL2increases from Ua to Ub. Then, when the age of service of vehicle 1Breaches the year 2y₀, the upper limit value UL2 increases from Ub to Uc.If any abnormality is not detected in battery 10, the upper limit valueUL2 increases from Uc to Ud when the age of use of vehicle 10 reachesthe year 3y₀.

Assume that abnormality of battery 10 is detected when the age ofservice of vehicle 1B is y₁ (2y₀<y₁<3y₀). For instance, in any of theplurality of cells 11, metal lithium precipitates, and the voltage valueoutput from monitoring unit 54 goes out of the normal range. Thus,abnormality of battery 10 is detected by abnormality detecting unit 121.

Here, charge ECU 48B lowers the upper limit value UL2 from Uc to Ub.After the upper limit UL2 is decreased from Uc to Ub, increase of upperlimit value UL2 is inhibited. Therefore, the upper limit value UL2 iskept at Ub. In the control shown in FIG. 23, when abnormality occurs inbattery 10, the level of upper limit value UL2 is returned to the lastlevel from the present level. The amount of decrease of upper limit UL2,however, is not limited.

FIG. 24 is a flowchart representing the control shown in FIG. 23.Referring to FIG. 24, at step S131, charge ECU 48B (abnormalitydetermining unit 121) determines whether or not any abnormality occurredin battery 10, based on detected values from monitoring unit 54. If itis determined that abnormality occurred in battery 10 (YES at stepS131), the process proceeds to step S132. At step S132, charge ECU 48B(control range setting unit 111B) lowers the upper limit value UL2. Atstep S133, chare ECU 48B inhibits increase of upper limit value UL2.

On the other hand, if the battery 10 is determined to be normal (NO atstep S131), the process proceeds to step S124. At step S134, charge ECU48B (control range setting unit 111B) maintains the upper limit value atthe current value. After the end of process step S133 or S134, theoverall process returns to the main routine.

(Second Control Pattern)

FIG. 25 is a graph representing a second control executed whenabnormality of battery 10 is detected. Referring to FIG. 25, if anyabnormality is not detected in battery 10, the upper limit value UL2increases at every y₀ years. In this point, the second control patternis the same as the first control pattern (see FIG. 23).

Assume that abnormality of battery 10 is detected when the age ofservice of vehicle 1B is y₂ (2y₀<y₂<3y₀). For instance, in any of theplurality of cells 11, metal lithium precipitates, and the voltage valueoutput from monitoring unit 54 goes out of the normal range, asdescribed above. Thus, abnormality of battery 10 is detected byabnormality detecting unit 121. When abnormality of battery 10 isdetected, charge ECU 48B inhibits increase of upper limit value UL2, andfixes the upper limit value UL2 at the present value. Then, the upperlimit value UL2 is kept at Uc.

In the control patterns shown in FIGS. 23 and 25, the amount of changeof the upper limit value when the upper limit value is increased may beconstant. Alternatively, as in Embodiment 2, the amount of change in theupper limit value may be made smaller as the number of increase of theupper limit value increases.

FIG. 26 is a first flowchart representing the control shown in FIG. 25.Referring to FIG. 26, at step S141, charge ECU 48B (abnormalitydetermining unit 121) determines whether or not any abnormality occurredin battery 10, based on detected values from monitoring unit 54. If itis determined that abnormality occurred in battery 10 (YES at stepS141), the process proceeds to step S142. At step S142, charge ECU 4813(control range setting unit 111B) inhibits increase of upper limit valueUL2.

On the other hand, if the battery 10 is determined to be normal (NO atstep S141), the process proceeds to step S143. At step S143, charge ECU48B (control range setting unit 111B) permits increase of upper limitvalue UL2. After the end of process step S142 or S143, the overallprocess returns to the main routine.

FIG. 27 is a second flowchart representing the control shown in FIG. 25.Referring to FIGS. 27 and 13, the flowchart of FIG. 27 is different fromthe flowchart of FIG. 13 in that it additionally includes the process ofstep S150. The process of step S150 is executed if it is determined atstep S101 that the age of service of the vehicle has reached thestandard value.

At step S150, charge ECU 48B determines whether or not the increase ofupper limit value UL2 is permitted. Based on the result of process shownin the flowchart of FIG. 26, charge ECU 48B determines whether or notthe increase of upper limit value UL2 is permitted.

If it is determined that the increase of upper limit value UL2 ispermitted (YES at step S150), the process proceeds to step S102.Therefore, the upper limit value increases. On the other hand, if it isdetermined that the increase of upper limit value UL2 is inhibited (NOat step S150), the process of step S104 is executed. At step S104,increase of upper limit value UL2 is prevented. Therefore, the upperlimit value UL2 is kept at the present value.

The process of steps S101, S102, S103 and S104 shown in FIG. 27 may bereplaced by the process of steps S101A, S102A, S103A and S104A shown inFIG. 14, respectively. Here, when the travel distance of the vehiclereaches the standard value (x₀) and the increase of upper limit valueUL2 is permitted, control range setting unit 111B increases the upperlimit value UL2. If the increase of upper limit value UL2 is inhibited,control range setting unit 111B fixes the upper limit value UL2 at thepresent value.

As described above, according to Embodiment 3, the upper limit value islimited so as not to exceed the standard value. The standard value isdetermined in advance to prevent overcharging of the battery. Therefore,according to Embodiment 3, even if the control for increasing the upperlimit value is executed repeatedly, overcharging of battery can beprevented. Therefore, deterioration of battery 10 is not intensified.

Further, according to Embodiment 3, if any abnormality of battery 10 isdetected, the charge ECU lowers the upper limit value. Therefore,continuous occurrence of abnormality in battery 10 can be prevented, andhence, deterioration of battery 10 can be reduced.

Further, according to Embodiment 3, if any abnormality of battery 10 isdetected, the charge ECU inhibits increase of the upper limit value.Thus, deterioration of battery 10 is not intensified.

[Other Examples of Vehicle Configuration]

In Embodiments 1 to 3, vehicles including only a motor as the drivingsource for generating the driving force have been described. The presentinvention, however, is applicable to a vehicle including a power storagedevice and an electric motor generating driving force from the electricpower stored in the storage device. Therefore, the present invention isapplicable, for example, to a hybrid vehicle including an engine and anelectric motor as driving sources.

FIG. 28 shows a configuration of a hybrid vehicle as an example of thevehicle in accordance with the present invention. Referring to FIGS. 28and 1, a vehicle 1C is different from vehicle 1 in that it additionallyincludes a converter (CONV) 14, an inverter 18, an MG 24, a power splitdevice 26, and an engine 28.

Engine 28 generates power by burning fuel such as gasoline. Converter 14converts DC voltage across positive electrode line 13P and negativeelectrode line 13N and DC voltage across positive electrode line 15P andnegative electrode line 15N to/from each other, based on the controlsignal PWC received from MG-ECU 30.

Inverter 18 has a structure similar to that of inverter 16 and realized,for example, by a three-phase bridge circuit. MG 24 is an AC rotatingelectrical machine, and it is implemented, for example, by a three-phaseAC synchronous electric motor having a rotor with a permanent magnetembedded. Inverter 18 drives MG 24 based on a control signal PWI2received from MG-ECU 30.

Driving shaft of MG 24 is coupled to power split device 26. Power splitdevice 26 includes a planetary gear mechanism including a sun gear, apinion gear, a planetary carrier and a ring gear. The rotation shaft ofMG 24, a crank shaft of engine 28 and a driving shaft coupled to drivingwheels 22 are connected to power split device 26. Power split device 26distributes the power output from engine 28 to MG 24 and driving wheels22. Thus, engine 28 can drive vehicle 1C.

In the configuration shown in FIG. 28, battery 10 can be charged bypower source 60 provided outside of vehicle 1C. Further, by the drivingforce of MG 20, vehicle 1C can travel with engine 28 stopped. Therefore,the present invention is applicable to vehicle 1C having theconfiguration shown in FIG. 28. It is noted that vehicle 1C may includecharge ECU 48A or 48B in place of charge ECU 48.

FIG. 28 shows a series/parallel type hybrid vehicle in which the powerfrom engine 28 can be transmitted to driving wheels 22 and MG20 by powersplit device 26. The present invention is also applicable to hybridvehicles of different types. By way of example, the present invention isapplicable to a so-called series type hybrid vehicle in which onlyengine 28 is used for driving MG24 and vehicle driving force isgenerated only by MG20.

Further, the present invention is also applicable to a fuel cell vehicleincluding a fuel cell as a DC power source in addition to battery 10.

In the embodiments of the present invention, lithium ion battery is usedas the power storage device for supplying electric power to the electricmotor. The application of the present invention, however, is not limitedto a vehicle using lithium ion battery. As long as a vehicle has a powerstorage device that may possibly be deteriorated when kept at the highSOC state and the vehicle has an electric motor of which driving forceis generated by the power storage device, the present invention isapplicable to such a vehicle.

Further, switching of charging mode may be automatically done by thecharge ECU. For instance, if the charging mode is set to the normal modeand the travel distance exceeds the standard value before the age oftravel reaches a prescribed number of years, the charge ECU may switchthe charging mode from the normal mode to the long life mode. Conditionsfor charge ECU to switch the charging mode are not specifically limited.

Further, in the present embodiment, the charge ECU is configured to beable to switch the charging mode between the normal mode and the longlife mode. The vehicle in accordance with the present invention,however, may have only the long life mode as the charging mode. In thiscase also, the charge ECU increases the upper limit value of the SOCcontrol range if prescribed conditions related to the deterioration ofbattery 10 are satisfied. Therefore, it becomes possible to preventdecrease of cruising distance (to ensure the target cruising distance orlonger) and to reduce deterioration of battery 10.

Even if the charging mode is only the long life mode, it is possible toset the amount of change of the upper limit value such that the upperlimit value is lower than a prescribed value. The prescribed value isdetermined in consideration of overcharge of the battery. In this case,though SOC reaches the upper limit value of SOC at the time of chargingthe battery, the upper limit does not exceed the prescribed value.Therefore, overcharge of the battery can be prevented.

The embodiments as have been described here are mere examples and shouldnot be interpreted as restrictive. The scope of the present invention isdetermined by each of the claims with appropriate consideration of thewritten description of the embodiments and embraces modifications withinthe meaning of, and equivalent to, the languages in the claims.

REFERENCE SIGNS LIST

1, 1A-1C vehicles, 10 battery, 11 cell, 12 system main relay, 13N, 15Nnegative electrode lines, 13P, 15P positive electrode lines, 14converter, 16, 18 inverters, 20, 24 motor generators, 22 driving wheels,26 power split device, 28 engine, 42 charge inlet, 43 sensor, 44charger, 46 relay, 48, 48A, 48B charge ECUs, 49 switch, 50 currentsensor, 54 monitoring unit, 56(1)-56(n) sensors, 58 analog-digitalconverter, 60 power source, 62 connector, 70 air conditioner, 101 SOCestimating unit, 111, 111A, 111B control range setting units, 112determining unit, 113 signal generating unit, 121 abnormalitydetermining unit, BB(1)-BB(n) battery blocks.

The invention claimed is:
 1. A vehicle, comprising: a power storagedevice configured to be rechargeable; an electric motor configured togenerate driving force for driving said vehicle by using electric powerstored in said storage device; a charging mechanism configured to supplyelectric power output from a power source outside said vehicle to saidpower storage device; and a controller configured to control state ofcharge of said power storage device when said power storage device ischarged, said controller including: a state estimating unit configuredto calculate an index value indicating said state of charge; a detectingunit configured to detect abnormality occurred in said power storagedevice, and a setting unit configured to increase an upper limit valueof said index value when prescribed condition related to deteriorationof said power storage device is satisfied, wherein said setting unit isconfigured to set an amount of change of said upper limit value suchthat possible distance of travel of said vehicle attains to a targetdistance or longer, to make smaller said amount of change as the numberof increase of said upper limit value increases, to increase said upperlimit value repeatedly until said upper limit value reaches a standardvalue, to maintain said upper limit value at said standard value oncesaid upper limit value reached the standard value, and to maintain saidupper limit value at a present value when said abnormality is detectedby said detecting unit.
 2. The vehicle according to claim 1, whereinsaid prescribed condition is determined in advance based on period ofuse of said vehicle.
 3. The vehicle according to claim 1, wherein saidprescribed condition is determined in advance based on travel distanceof said vehicle.
 4. The vehicle according to claim 1, wherein saidsetting unit is capable of switching between a first mode having saidupper limit value fixed and a second mode allowing adjustment of saidupper limit value, and sets said amount of change in said second mode.5. The vehicle according to claim 4, further comprising: a commandgenerating unit configured to switch between generation of a command toextend a useable period of said power storage device and stopping ofgeneration of said command, by a manual operation, wherein said settingunit selects said second mode from said first and second modes when saidcommand generating unit generates said command, and selects said firstmode from said first and second modes when said command generating unitstops generation of said command.
 6. The vehicle according to claim 1,wherein said controller further includes: a detecting unit configured todetect any abnormality occurring in said power storage device; and saidsetting unit is configured to lower said upper limit value when saidabnormality is detected by said detecting unit.
 7. A method ofcontrolling a vehicle, wherein said vehicle includes: a power storagedevice configured to be rechargeable; an electric motor configured togenerate driving force for driving said vehicle by using electric powerstored in said storage device; a charging mechanism configured to supplyelectric power output from a power source outside said vehicle to saidpower storage device; and a controller configured to control state ofcharge of said power storage device when said power storage device ischarged, said method comprising the steps of: calculating an index valueindicating said state of charge; and increasing an upper limit value ofsaid index value when prescribed condition related to deterioration ofsaid power storage device is satisfied, wherein at said step ofincreasing the upper limit value, an amount of change of said upperlimit value is set such that possible distance of travel of said vehicleattains to a target distance or longer; said control method furthercomprising the steps of: making smaller said amount of change as thenumber of increase of said upper limit value increases; limiting saidupper limit value so that said upper limit value does not exceed astandard value when said upper limit value is increased repeatedly;detecting any abnormality occurring in said power storage device; andfixing said upper limit value at a present value said abnormality isdetected.
 8. The vehicle control method according to claim 7, whereinsaid prescribed condition is determined in advance based on period ofuse of said vehicle.
 9. The vehicle control method according to claim 7,wherein said prescribed condition is determined in advance based ontravel distance of said vehicle.
 10. The vehicle control methodaccording to claim 7, further comprising the step of: selecting one of afirst mode having said upper limit value fixed and a second modeallowing adjustment of said upper limit value, wherein at said step ofincreasing said upper limit value, said amount of change is set whensaid second mode is selected.
 11. The vehicle control method accordingto claim 10, wherein said vehicle further includes: a command generatingunit configured to switch between generation of a command to extend auseable period of said power storage device and stopping of generationof said command, by a manual operation; and at said step of selecting,said second mode is selected from said first and second modes when saidcommand generating unit generates said command, and said first mode isselected from said first and second modes when said command generatingunit stops generation of said command.
 12. The vehicle control methodaccording to claim 7, further comprising the steps of: detecting anyabnormality occurring in said power storage device; and lowering saidupper limit value when said abnormality is detected.